KillAura's shield-break weapon check doesn't verify the axe is actually equippable/available

[hokindo9000]

Describe the bug

In KillAura.java, acceptableWeapon() checks shouldShieldBreak() first:

private boolean acceptableWeapon(ItemStack stack) {
    if (shouldShieldBreak()) return stack.getItem() instanceof AxeItem;
    ...
}

This correctly requires the currently held item to be an axe when shield
breaking is active. However, in the main onTick() logic, auto-switch only
swaps to an axe if one is found:

if (shouldShieldBreak()) {
    FindItemResult axeResult = InvUtils.find(itemStack -> itemStack.getItem() instanceof AxeItem, 0, 8);
    if (axeResult.found()) weaponResult = axeResult;
}

If auto-switch is OFF (or no axe exists in the hotbar) while shield-break
mode is active and the player is not already holding an axe,
acceptableWeapon() will correctly return false via shouldShieldBreak()'s
branch - causing KillAura to call stopAttacking() every tick with no
attack ever occurring, and no feedback/warning shown to the user about
why KillAura appears to silently do nothing against a blocking target.

Steps to reproduce

1. Enable KillAura, set Shield Mode to "Break", disable Auto Switch (or
   ensure no axe is present in the hotbar).
2. Target a player who is actively blocking with a shield.
3. Observe KillAura does not attack and gives no indication that it's
   because no axe is available for shield breaking.

Meteor Version

26.1.2-42

Minecraft Version

26.1.2

Operating System

Linux

Before submitting a bug report

• This bug wasn't already reported (I have searched bug reports on GitHub).

• This is a valid bug (I am able to reproduce this on the latest dev build).